Cadmium free, environmentally friendly. Aluminum: For salt and brackish water. Conform to: Mil-Spec A-24779(SH) Magnesium: For freshwater only. Conform to: Mil-Spec A-21412(SH Includes: Skeg anode (1)Bar anode for Bracket (1)Block anode for lower unit (2)Block anode for lower unit (2)